Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$224.61	10.212%	$247.5472	$247.55	$247.55	$247.50
Purchase #2	$175.94	11.705%	$196.5338	$196.53	$196.55	$196.50
Purchase #3	$65.63	10.625%	$72.6032	$72.60	$72.60	$72.60
Purchase #4	$75.55	3.357%	$78.0862	$78.09	$78.10	$78.10
Purchase #5	$12.96	9.640%	$14.2093	$14.21	$14.20	$14.20
Purchase #6	$91.45	10.563%	$101.1099	$101.11	$101.10	$101.10
Purchase #7	$238.97	3.562%	$247.4821	$247.48	$247.50	$247.50
7 purchase totals =	$885.11		$957.5717	$957.57	$957.60	$957.50